Oxbridge Medicine Academic Questions

Consider things that we class as drugs e.g. paracetamol and what we don't class as drugs e.g. water

Drugs don't have to necessarily have to be external to the body e.g. insulin injections are classed drugs but insulin is hormone made naturally by the body

All 'drugs' seem to have something in common - they interact with major biological molecules in the body

Examples to illustrate would be good:
 - Proteins: enzyme inhibitors such as aspirin
 - DNA: chemotherapy drugs e.g. cisplatin

Typically have a therapeutic effect by affecting a physiological state

Immediate changes - reduction in blood volume

How would the body respond to this?

Reasonable to suggest that it has to make sure that important organs are still perfused properly and it would prioritise conserving water

Downstream effects - increase in heart rate, vasoconstriction to maintain blood pressure

Could suggest hormones responsible for this such as adrenaline

To conserve water the blood flow to the kidney would be reduced

Increase in feeling of thirst

SARS-CoV-2 is an RNA virus which translates its RNA into proteins upon infecting cells while also replicating its RNA

mRNA in the vaccine contains code for the spike protein - the virus uses this to enter cells

First the vaccine has to get into cells - it has to cross the cell membrane barrier

In some vaccines the mRNA has a lipid coat to enable it enter without needed a protein

Once translated the spike protein has to be recognised by the immune system - the cell achieves this by presenting it on its surface

This stimulates the production of antibodies which are specific to the spike protein

They prevent the spike protein from binding to its receptor

There's no right answer here, consider the function of different organs and what would happen to the body without them

Brain - processing of sensory information, generating motor commands, source of emotions, consciousness etc. Legal death is brain death therefore a favourite?

Heart - pumping of blood to rest of body, without it other organs would die from hypoxia due to lack of oxygen

Lungs - gas exchange surface, needed to get rid of carbon dioxide and take in oxygen for cells to respire

Kidneys - osmoregulation, filtering of the blood. It's possible to live with just one so this suggests it's not as important as the others

Liver - metabolism of harmful substances in the blood, filtering of substances, production of bile etc.

Not all DNA forms part of of the coding sequence for proteins hence the term 'junk'

While it's referred to as junk DNA, it is still important to suggest their purpose for being in the genome

Within genes there are introns which are spliced out during post-transcriptional modification of RNA

Exons can be arranged in different ways which increases the diversity of proteins which can be generated from the same gene

Sequences upstream of the gene are needed to recruit RNA polymerase and transcription factors e.g. the promoter sequence

Part of the DNA is required to recruit ribosomes when transcribed into mRNA (ribosome binding site)

Some parts of the DNA have unknown function e.g. repetitive elements

Some DNA sequences are remnants of past retroviral infections which have remained integrated into the genome

Think about the main functions of a placenta and suggest features accordingly

Each feature performs a function that the fetus' organs will perform post-natally (in brackets)

Gas exchange surface - high surface area with rich blood supply to maximise transfer of oxygen from mother to fetus (lungs)

Excretory functions, water balance, pH regulation - need someway to remove waste products from fetus (kidney)

Synthetic and secretory functions - useful to coordinate pregnancy changes in mother and fetus since it acts as the interface between the two (most endocrine glands)

Immunological interactions and protection - the fetus is a foreign body so placenta needs to ensure that the mother doesn't reject the fetus during pregnancy

Glucose is the substrate for respiration - cancer cells require more since they are constantly growing unregulated by the cell cycle

Glucose eventually used to generate ATP

ATP drives biosynthetic pathways such as nucleotide synthesis which cancer cells will be doing lots of

Gives the cancer cell an evolutionary advantage over other cells if it's able to divide more

It's a good idea to first outline how to describe the position of a sound in space

(1) Vertical plane - elevation

(2) Horizontal plane - azimuth

The external ear itself (pinna) can affect elements of the sound depending on its elevation

This is interpreted by the brain - how might this 'interpretation' work?

Since we have 2 ears it would be reasonable to suggest that there is a time delay in the detection of sound between one ear and the other depending on the position of the sound in the horizontal plane

This time delay can be used as a signal by the brain to locate sounds

In addition, the head provides an acoustic shadow which reduces the intensity of sounds depending on which side of the head it originated from

This difference in intensity between the 2 ears can also be used as a signal to pinpoint the location of a sound

At altitude there is a reduction in barometric pressure

This causes a reduction in the inspired partial pressure of oxygen (pO2) leading to hypoxia

To compensate for this people tend to hyperventilate to increase their pO2

However, this reduces their pCO2 since they are exhaling more CO2; this causes an increase in the pH of their cerebrospinal fluid (CSF)

Changes in the composition of CSF brings pH back to normal

Oxygen diffusion can be rate-limiting at altitude because there is a suppressed partial pressure gradient of oxygen

Therefore, it takes longer for oxygen to diffuse into the blood

Finally there is an increase in the concentration of 2,3-DPG which causes a right shift in the oxygen dissociation curve

This facilitates unloading of oxygen since it has a lower affinity to haemoglobin

For permanent residents at high altitude there is a physiological adaptation that occurs to increase oxygen content - a significant increase in the concentration of haemoglobin (polycythemia)

Antibiotic - drugs used to kill microorganisms e.g. bacteria

Anticancer - drugs used to treat cancer

Main difference is in target: pathogens vs cancerous cells

Different mechanisms of action, suggest some examples:
 - Antibiotics can target cell walls (bacteria), lipid within membranes (fungi), enzymes needed for replication (viruses), DNA etc
 - Anticancer drugs can be broadly split into cytotoxic and molecular targeted drugs
  - Cytotoxic drugs can target: DNA and its synthesis, enzymes needed for DNA replication, the mitotic spindle etc
  - Molecular targeted drugs can target: receptors, tyrosine kinases, hormone synthesis and many more

Improvements in these drugs mostly come from making them more selective, particularly with anti-cancer drugs because they can be very toxic

New drugs are also designed to counteract antibiotic resistance, making better antibiotics may include changing their structure so they bind with higher affinity to their targets

Anti-cancer drugs can be made better by targeting molecules/markers specific to the cancer cell

Some drugs upregulate the immune response (T cells in particular) to cancer by binding to certain inhibitory molecules on cancer cells, these have shown to be effective in some cancers